KR20210118837A - Polycrystalline silicon mass, its package and its manufacturing method - Google Patents

Abstract

An object of the present invention is to suppress the occurrence of unevenness in a polycrystalline silicon mass packaged in a resin bag, even if it is stored for a long period of time and exposed to a high-temperature and high-humidity environment during transportation.
The polycrystalline silicon mass package according to the present invention is a package in which a polycrystalline silicon mass having a surface metal concentration of 1000 pptw or less is filled in a resin bag, and the amount of nitrate ions and preferably the amount of fluorine ions present in the package is packaged It is characterized in that the amount is 50 μg/L or less, respectively, with respect to the filled voids of the polycrystalline silicon mass formed when the sieve is placed under 25° C. and 1 atm.

Description

Polycrystalline silicon mass, its package and its manufacturing method

The present invention relates to a polycrystalline silicon mass, a package thereof, and a manufacturing method thereof.

High-density integrated electronic circuits require high-purity single-crystal silicon wafers. A single crystal silicon wafer can be obtained by cutting out from a single crystal silicon rod manufactured by the CZ method (Czochralski method). Polycrystalline silicon called polysilicon is used as a raw material for manufacturing this CZ method single crystal silicon rod.

As a method for producing polycrystalline silicon, the Siemens method is known. In the Siemens method, a silicon core wire disposed inside a bell jar-type reaction vessel is heated to the precipitation temperature of silicon by energizing, and a silane compound such as _{trichlorosilane (SiHCl 3} ) or monosilane (SiH _{4 ) is heated here.} Gas and hydrogen are supplied, and polycrystalline silicon is deposited on a silicon core wire by a chemical vapor deposition method to obtain a high-purity polycrystalline silicon rod.

The obtained polycrystalline silicon rod is cut or crushed into a size that is easy to handle as a raw material for manufacturing single crystal silicon in the CZ method. Specifically, a polycrystalline silicon rod is cut or crushed by a cutting or crushing mechanism made of a hard metal to obtain a polycrystalline silicon mass (cut rod, crushed product). Here, since a tungsten carbide/cobalt alloy (WC/Co alloy) is usually used as the hard metal constituting the cutting mechanism or the crushing mechanism, the surface of the polycrystalline silicon mass is contaminated with tungsten or cobalt. In addition, the surface of the polycrystalline silicon mass is contaminated with various other metallic impurities due to contact with various metal tools such as a transfer mechanism and a classifier. Thus, even a small amount of these metal impurities causes defects in single crystal silicon wafers used in high-density integrated electronic circuits, which ultimately deteriorate device performance and limit circuit density.

For this reason, in a polycrystalline silicon mass, it is necessary to reduce the metal impurity concentration on the surface as much as possible, and it is carried out to remove this by carrying out pickling. Specifically, the etching process with a hydrofluoric acid aqueous solution is performed. Here, hydrofluoric acid has the effect of dissolving the oxide film formed on the surface of the polycrystalline silicon crushed mass favorably and also dissolving various metals and oxides thereof adhering thereto. In addition, nitrate oxidizes polycrystalline silicon, forms an oxide film on the surface of the polycrystalline silicon fracture, and has an effect of accelerating dissolution and removal of the oxide film by the hydrofluoric acid.

In this way, after the surface of the polycrystalline silicon mass has been cleaned, it is packaged in a resin bag and stored in the form of a package in order to prevent re-contamination on the surface of the mass after the washing process and drying process, and then the single crystal silicon rod It is transported and shipped to manufacturing plants such as At this time, one of the problems which arises in the polycrystalline silicon mass filled in a package is generation|occurrence|production of the unevenness on the surface (refer patent document 1). In particular, when the package is stored for a long time or exposed to a high temperature and high humidity environment (severely, at a temperature of 50 ° C or higher and a humidity of 70% or higher) during transportation, the problem that a large number of stains occurs on the surface of the filled polycrystalline silicon mass is present. there was.

Here, the unevenness is an abnormal growth of an oxide film on the surface of polycrystalline silicon, and when the polycrystalline silicon mass generated from this is used as a raw material for growing single crystal silicon, defects occur in the cut out silicon wafer, resulting in deterioration of quality. It is thought that the cause of the occurrence is that the acid liquid component (fluorine ion or nitrate ion) used in the pickling process permeates and remains inside the cracks or cracks on the surface of the mass. That is, these acid liquid components that have penetrated deeply into cracks or crevices cannot be sufficiently removed even by washing the polycrystalline silicon mass with water. It is presumed to cause the stain by binding.

For this reason, in Patent Document 1, in order to reduce the residual fluorine component due to insufficient water removal, it is proposed that the polycrystalline silicon mass is pickled and dried, and then maintained at a temperature of 45° C. or higher under reduced pressure for a certain period of time. However, it is described that the effect of reducing the fluorine component is saturated at a heating temperature of 60° C. or higher, and 70° C. or less is preferable in view of an increase in heating cost (refer to paragraph [0025]). Moreover, the temperature conditions in the drying process of the preceding stage are not shown at all either.

Moreover, in patent document 2, in the polycrystalline silicon lump after acid washing, it is tried to hold|maintain this in pure water vapor|steam, and to wash|clean with the condensed water which arose on the surface, and to remove the said acid-liquid component. However, even in this case, even if the said pure water vapor is high temperature, it is the condensed water that washes the acid liquid component, and the temperature is only much less than 100 degreeC.

[Patent Document 1] Japanese Patent Laid-Open No. 2009-298672 [Patent Document 2] Japanese Patent Laid-Open No. 5-121390

By applying such a conventional method for removing the acid solution component, the acid solution component adhering to the surface of the polycrystalline silicon mass after acid washing can be removed quite favorably. In particular, as shown in Patent Document 1, the removability of the fluorine component is stably high, and even those penetrating into the cracks or cracks can be considerably removed, and the suppression of the occurrence of stains in the polycrystalline silicon mass obtained by this is degree is achieved.

However, in the package filled with the resin bag, from the viewpoint of being stored for a long period of time and exposed to a high-temperature and high-humidity environment during transportation, it cannot be said that the improvement effect is sufficient. In particular, with the recent densification of integrated electronic circuits, the demand for defect prevention for single-crystal silicon wafers is increasing more and more. A high degree of restraint was strongly demanded.

In view of the said subject, the present inventors have continued earnest examination. As a result, in the polycrystalline silicon mass that has been pickled with an aqueous hydrofluoric acid solution, the occurrence of stains cannot be completely suppressed when it is made into a package. It has been found that the removal of nitrate ions in the residual acid liquid component is caused by insufficient. Then, based on this knowledge, it was found that the concentration of nitrate ions in the filled pores of the polycrystalline silicon mass in the case of a packaged body directly affects the occurrence of stains, and the present invention was completed.

That is, the present invention provides a package in which a polycrystalline silicon mass having a surface metal concentration of 1000 pptw or less is filled in a resin bag, wherein the amount of nitrate ions present in the package is formed when the package is placed at 25° C. and 1 atmosphere. It is a polycrystalline silicon mass packaged body characterized in that the amount is 50 µg/L or less with respect to the filled voids of the polycrystalline silicon mass to be used.

The present invention also provides a polycrystalline silicon mass having a surface metal concentration of 1000 pptw or less and a surface nitrate ion content of 1.0×10 ^-4 µg/mm ^{2 or less.} This polycrystalline silicon mass can be advantageously used to obtain the polycrystalline silicon mass package by filling a resin bag.

In addition, the present invention also provides a method of drying the polycrystalline silicon mass cleaning body pickled with an aqueous hydrofluoric acid solution at a heating temperature of 100° C. or higher as a method for manufacturing the polycrystalline silicon mass.

Further, according to the present invention, when the polycrystalline silicon mass obtained by the above method is packaged in a resin bag, the amount of nitrate ions present inside the package is a polycrystalline silicon mass formed when the package is placed at 25° C. and 1 atmosphere. It also provides a method for producing the polycrystalline silicon mass package, characterized in that the packaging is performed at a filling amount of 50 μg/L or less with respect to the filled pores of water.

The polycrystalline silicon mass packaged body of the present invention is a polycrystalline silicon mass filled therein, and unevenness is hardly generated on the surface. In particular, even if the package is stored for a long period of time and placed in a harsh environment such as being exposed to a high temperature and high humidity environment during transportation, the occurrence of stains in the polycrystalline silicon mass is highly suppressed.

Therefore, when this polycrystalline silicon mass is used as a raw material for single crystal silicon growth, the generation of defects in the cut out silicon wafer can be effectively prevented, which is very important industrially.

In the polycrystalline silicon mass package of the present invention, the polycrystalline silicon mass filled in the resin bag is a mass obtained by cutting or crushing a polycrystalline silicon rod to a size that is easy to handle for use as a raw material for manufacturing single crystal silicon in the CZ method or the like. and so-called cut rods and crushed objects. The polycrystalline silicon rod is not limited in its manufacturing method, but is usually manufactured by the Siemens method. Here, the Siemens method is a method of vapor-phase growth (precipitation) of polycrystalline silicon on the surface of a silicon core wire by a CVD (Chemical Vapor Deposition) method by bringing a silane source gas such as trichlorosilane or monosilane into contact with a heated silicon core wire. am.

The polycrystalline silicon rod obtained in this way has a substantially cylindrical shape, and the diameter thereof is not particularly limited, but is usually 80 to 150 mm. Also, the length of the polycrystalline silicon rod is not particularly limited, and is usually 1000 mm or more.

When the polycrystalline silicon mass is a cut rod, the polycrystalline silicon rod is cut to a predetermined length by a cutting mechanism to obtain a cylindrical body.

On the other hand, when the polycrystalline silicon mass is a crushed material, the polycrystalline silicon rod or a cut rod obtained therefrom may be crushed by a crushing mechanism. This crushing may be obtained by using a hammer, jaw crusher, or the like in which the striking part is made of a hard metal such as the WC/Co alloy, and if necessary, by classifying it to a desired size by a classification device such as a sieve or a step deck.

The size of the crushed material is preferably in the range of at least 90% by weight of the major axis of 2 to 160 mm. In this range, it is generally classified according to the particle size, and specifically, at least 90% by weight is within the range of 90 to 160 mm in length of the major axis, at least 90% by weight is within the range of 10 to 120 mm in length of the major axis, at least 90% by weight of the long axis is in the range of 10 to 60mm, or at least 90% by weight is the length of the major axis is in the range of 2 to 10mm, and the like.

The polycrystalline silicon mass obtained by cutting or crushing in this way is due to the cutting or crushing mechanism in contact with it, and the surface thereof is contaminated by tungsten or cobalt, and it is also in contact with various metal tools such as a conveying device or a classifier. As a result, it is contaminated with various other metal impurities. Thus, since these metal impurities need to be reduced as much as possible in single crystal silicon wafer applications as described above, the polycrystalline silicon mass is subjected to acid cleaning to etch the surface. In this way, in order to etch the surface of the polycrystalline silicon mass, it is necessary to use an aqueous nitric acid solution as the pickling solution, and it is preferable to also carry out dissolution and removal of the oxide film formed on the surface of the polycrystalline silicon mass, and this action is Since it has, it is more preferable to use an aqueous hydrofluoric acid solution.

In the hydrofluoric acid aqueous solution, the mixing ratio of each component may be appropriately determined according to the state of the polycrystalline silicon mass, pretreatment conditions, etc., but it is preferable to set it as the following mixing ratio. Specifically, it is preferable to contain 1 to 20 parts by weight of hydrogen fluoride and 150 to 250 parts by weight of nitric acid with respect to 100 parts by weight of water. As for hydrogen fluoride, it is more preferable that it is 1.5-15 weight part, and it is still more preferable that it is 4-6 weight part. Moreover, it is preferable that the weight ratio of nitric acid with respect to hydrogen fluoride (weight of nitric acid/weight of hydrogen fluoride) is 10-170 among these mixing ratios.

By acid washing using such an aqueous nitric acid solution, the surface metal concentration of the polycrystalline silicon mass is reduced to 1000 pptw or less, preferably 100 pptw or less, more preferably 80 pptw or less. In addition, although the lower limit of the surface metal concentration is 0 (zero) ideally, it is 10 pptw or more normally, Preferably it is 30 pptw or more. Here, the elements subject to the surface metal concentration of the polycrystalline silicon mass are 14 elements: Na, Mg, Al, K, Ca, Cr, Fe, Ni, Co, Cu, Zn, W, Ti, and Mo, displayed in total.

In the present invention, the surface metal concentration of the polycrystalline silicon mass is a value in which the weight of each metal contained in the polycrystalline silicon mass is expressed as the content per weight of the polycrystalline silicon mass (pptw), and is a value measured by the following method say That is, in the analysis of the metal concentration on the surface of the polycrystalline silicon mass to be measured, the surface of the polycrystalline silicon mass is etched, and each metal element in the obtained sample solution is analyzed and quantified by inductively coupled plasma mass spectrometry (ICP-MS). Specifically, if the polycrystalline silicon mass is a crushed material, about 40 g of the crushed material is transferred to a 500 ml clean polytetrafluoroethylene beaker, and 100 ml of the solution (50 wt%-HF: 10 ml, 70 wt%-nitric acid: 90 ml) is added. to perform extraction at 25° C. for 30 minutes. The liquid in the beaker and the washing solution obtained by washing the surface of the crushed polycrystalline silicon material with 100 ml of ultrapure water are transferred to a clean polytetrafluoroethylene beaker to obtain a surface extract of the crushed polycrystalline silicon material. Thus, the surface extract was evaporated to dryness, and a 3.5 wt%-nitric acid solution was added to the residue to make a constant volume of 20.0 ml, and the ICP-MS measurement was performed to obtain Na, Mg, Al, K, Ca, Cr, Measure the weight of each surface metal of Fe, Ni, Co, Cu, Zn, W, Ti, and Mo. The surface metal concentration of the crushed polycrystalline silicon material is obtained by dividing the measured value of each surface metal weight by the weight of the crushed material (about 40 g) to obtain the content (pptw) per unit weight of the crushed polycrystalline silicon material.

Even if it is a polycrystalline silicon lump in which the surface metal concentration is reduced by acid washing in this way, the occurrence of defects in the silicon wafer cut out as described above cannot be sufficiently prevented in single crystal silicon manufactured using this as a raw material. One of the major causes is due to the occurrence of stains due to the acid component remaining in the acid washing process, which is the same as described above even when heat treatment at a relatively low temperature or washing with condensed water in the prior art is performed. It cannot be highly suppressed together. This is because a significant amount of nitrate ions remain on the surface of the agglomerate in the heat treatment at low temperature or washing with condensed water. This is because it becomes a high concentration in the filled pores, which is included in the dew condensation generated by the temperature change in the package and attaches to the polysilicon mass again, forming an oxide film on the surface of the polysilicon mass.

On the other hand, in the present invention, polycrystalline silicon having a very low concentration of nitrate ions with respect to the filled pores in storage by using the polycrystalline silicon mass with a highly reduced amount of surface nitrate ions and filling it in a resin bag with sufficient filled pores. It is characterized in that it was made into a mass package. Specifically, the amount of nitrate ions present inside the package is a low level of 50 μg/L or less with respect to the filled pores of the polycrystalline silicon mass formed when the package is placed at 25° C. and 1 atm. This low level Due to the amount of nitrate ions, the reaction of forming an oxide film that causes unevenness on the surface of the polycrystalline silicon mass is significantly lowered. It is possible to obtain a polycrystalline silicon agglomerate as low as 5 μg/L or less in the amount of nitrate ions with respect to the above-mentioned filled pores. In addition, although the lower limit of the amount of nitrate ions with respect to the relevant filled pore is 0 microgram/L ideally, it is normally 1 microgram/L, More preferably, it is 2 micrograms/L. Here, when the amount of nitrate ions with respect to the filled pores becomes higher than 50 μg/L, the storage of the package is prolonged or staining occurs remarkably in a high-temperature and high-humidity environment.

In the present invention, the amount of nitrate ions and fluorine ions present in the package can be obtained by the following method. That is, at 25°C and room temperature under 1 atm, ultrapure water at 25°C is injected into the polycrystalline silicon mass package filled with the polycrystalline silicon mass, and a sufficient amount to immerse the surface of the polycrystalline silicon mass is injected and sealed, and nitric acid The component and the fluorine component are eluted. The injected amount of this pure water is generally 20 mL or more, more preferably 30 to 60 mL, per volume (L) of the resin bag, for example, a volume of about 3 L, which is a typical size of the polycrystalline silicon mass package. In the case of a package filled in a resin bag (normally filled with 5 kg of polycrystalline silicon mass), it is preferable to inject 100 mL. If the injection amount is increased too much, the concentration of the acid liquid component in the effluent decreases, so that the measurement sensitivity in the ion chromatograph decreases.

The polycrystalline silicon mass package into which this ultrapure water was poured was stirred or shaken for 5 minutes, and the nitric acid component and fluorine component inside the package were eluted into the water. The eluted water is collected, and the amount of nitrate ions and the amount of fluorine ions (μg) are measured by ion chromatography. Thus, by dividing the amount of nitrate ions and the amount of fluorine ions by the filled void volume of the polycrystalline silicon mass package, the amount of each ion (μg/L) with respect to the filled void can be obtained.

In addition, in the present invention, the filled pore volume (L) of the polycrystalline silicon mass package ^{is calculated by dividing the weight of the filled polycrystalline silicon mass by the density of polycrystalline silicon 2330 kg/m 3} The volume of the polycrystalline silicon mass is calculated, 25 It can be calculated|required by subtracting from the internal volume (L) of the resin bag which forms the package under °C and 1 atm.

In the present invention, in order to further improve the effect of inhibiting the occurrence of stains, the amount of fluorine ions present inside the package is also 50 μg with respect to the filled pores of the polycrystalline silicon mass formed when the package is placed at 25° C. and 1 atm. It is more preferable that it is a low level of the quantity used as /L or less, and it is especially preferable that it is a low level of the amount used as 30 micrograms/L or less. Since making the amount of fluorine ions too low also causes manufacturing difficulties, the lower limit of the amount of fluorine ions with respect to the above-mentioned filled pores is ideally 0 µg/L, but is usually 15 µg/L, and more preferably 20 µg/L.

In such a polycrystalline silicon mass package, it is preferable that the filled porosity of the resin bag is 40 to 70%. When the filled porosity is less than 40%, it is difficult to adjust the amount of nitrate ions to the filled voids within the above range. The efficiency of storage and transport is reduced.

For the same reason, the total amount of nitrate ions and fluorine ions present inside the package is 100 μg/L or less with respect to the filled voids of the polycrystalline silicon mass formed when the package is placed at 25° C. and 1 atm. It is more preferable that it is a level, and it is especially preferable that it is a low level of the amount used as 70 micrograms/L or less. Since making the total amount of nitrate ions and fluorine ions too low also causes manufacturing difficulties, the lower limit of the total amount of nitrate ions and fluoride ions in the above-mentioned filled voids is ideally 0 μg/L, but is usually 16 μg/L, more preferably Usually 22 μg/L.

In addition, the polycrystalline silicon mass filled into the package as described above preferably has a surface metal concentration of 1000 pptw or less, and ^{a low level of surface nitrate ion content of 1.0 × 10 -4} μg/mm ² or less, and further, The amount of surface nitrate ions is more preferably a low level of ^{1.0×10 -5} μg/mm ^{2 or less.} Further, the lower limit of the bulk polycrystalline silicon surface of the water to nitric acid ion amount filled in the package body, but is ideally 0μg / mm ^2, is usually ^{1.0 × 10 -6 μg / mm 2} , and more preferably 2.0 × 10 ^-6 μg / mm ² is

Further, the amount of surface fluorine ions is preferably 1.0×10 ⁻⁴ μg/mm ² or less, and more preferably, the amount of surface fluorine ions is at a low level of ^{6.0×10 −5} μg/mm ^{2 or less.} Further, the lower limit value of the polycrystalline silicon lump water surface fluoride ion amount of filling in the package, but ideally 0μg / mm ^2, and typically ^{3.0 × 10 -5 μg / mm 2} , more preferably from 4.0 × 10 ^-5 μg / It is mm ^2.

Further, the total amount of surface nitrate ions and surface fluorine ions ^{is preferably 2.0×10 −4} μg/mm ² or less, and more preferably a low level of ^{7.0×10 −5} μg/mm ^{2 or less.} Further, the lower limit of the total amount of the poly-Si surface of the water bulk nitrate ions and fluoride ions to the surface charge on the package body, but is ideally 0μg / mm ^2, and typically ^{3.1 × 10 -5 μg / mm 2} , more preferably 4.2 ×10 ^-5 μg/mm ² .

Here, the amount of surface nitrate ions and the amount of surface fluorine ions in the polycrystalline silicon mass can be obtained by the following method. That is, a resin bag having a volume of about 3 L is filled with about 5 kg of a polysilicon mass, and a polysilicon mass package for surface concentration measurement is obtained. 100 mL of ultrapure water of the same temperature was injected into the polycrystalline silicon mass package for surface concentration measurement at 25°C and room temperature under 1 atm pressure, sealed, stirred or shaken for 5 minutes, and the nitric acid component and fluorine component inside the package were removed Elution into the water. The eluted water is collected, and the amount of nitrate ions and the amount of fluorine ions (μg) are measured by ion chromatography. Then, by dividing the amount of these nitrate ions and the amount of fluorine ions by the surface area S (mm ² ) of the polycrystalline silicon mass used for measurement, the abundance per unit surface area of each of these ions can be calculated.

In the present invention, the surface area of the polycrystalline silicon lump of water S (mm ²⁾ can be determined by the following method. That is, by measuring the total number A of polycrystalline silicon mass packaged in a resin bag, and dividing the total weight by the total number A, the average weight W (g/piece) per polycrystalline silicon mass is obtained, and the average weight W (g/piece), density rho = 2330 kg/m ³ of polycrystalline silicon, and total number A, in cube conversion, can be calculated|required by the following formula.

S(mm ² ) = W/ρ^ (2/3) × 6 × A × 100 (mm ² /cm ² )

For the resin bag, a resin material such as polyethylene, polypropylene, polyvinyl chloride, or nylon may be used. As for the shape, a shape such as a flat bag or a gadget bag is generally adopted, and a double encapsulation structure in which the bag is doubled is preferably used. In addition, in order to suppress friction or breakage between the polycrystalline silicon mass and the packaging material, it is also a preferable embodiment to reduce the pressure or vacuum the inside of the package.

Next, a method for manufacturing the polycrystalline silicon mass packaged body of the present invention will be described. When the polycrystalline silicon mass package of the present invention has a surface metal concentration of 1000 pptw or less, when it is packaged in a resin bag, the manufacturing method is limited as long as the amount of nitrate ions to the filled voids is lowered. it's not going to be Preferably, it can be produced by drying the polycrystalline silicon mass washing body acid-washed with an aqueous hydrofluoric acid solution at a heating temperature of 100° C. or higher.

The acid washing process with hydrofluoric acid aqueous solution is as described above. What is necessary is just to carry out washing|cleaning by injecting|throwing-in the polycrystalline silicon mass into the resin basket excellent in chemical-resistance, and immersing in the hydrofluoric acid aqueous solution in a washing tank. As the resin used as the material of the basket, for example, polypropylene, polyethylene, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF) are used. The washing tank may be provided in one set or in plurality.

It is preferable that the washing|cleaning body of the polycrystalline silicon mass which has finished acid washing with the said hydrofluoric acid aqueous solution is washed with water and dried. Although water washing is performed to remove the etchant adhering to the surface of the polycrystalline silicon mass, it cannot sufficiently remove the residual acid component, particularly the nitric acid component, penetrating into the cracks or cracks.

As for water for water washing, it is preferable to use ultrapure water from a viewpoint of a metallic foreign material. Moreover, you may provide one set or a plurality of washing tanks. Next, in order to increase the drying efficiency in the drying process, it is more preferable to manage at least the temperature of the final water washing tank at 60°C or higher, more preferably 80°C or higher, and raise the temperature of the polycrystalline silicon mass.

In this way, the polycrystalline silicon mass cleaning body acid-washed with an aqueous hydrofluoric acid solution is dried at a heating temperature of 100 DEG C or higher. As described above, since the temperature of the gas to be contacted in the drying process is at a high temperature of 100° C. or higher, the polycrystalline silicon mass cleaning body to which it is sprayed is also heated to the same temperature. As a result, in the residual components of the aqueous hydrofluoric acid solution adhering to the polycrystalline silicon mass cleaning body, not only fluorine ions but also nitrate ions can be volatilized at a high rate, and these acid solution components penetrating inside cracks or cracks are highly removed. can be removed By filling the dried polycrystalline silicon mass into the resin bag, it becomes possible to obtain a polycrystalline silicon mass package with an extremely low amount of nitrate ions in the filled pores.

Here, the hydrofluoric acid aqueous solution has a concentration of 68% by weight of nitric acid and is azeotroped at a temperature of 120°C, so that the heating temperature is preferably 120°C or higher. Further, if the heating temperature is too high, the deterioration of members such as resin inside the device is accelerated, so it is preferably 150° C. or less.

The gas supplied for drying is usually air, but may be an inert gas such as nitrogen or argon. As the feed gas, one that is as clean as possible is used, and preferably one with a purity level of class 100 or less is used.

The drying time may be appropriately set so as to achieve the desired amount of nitrate ions in consideration of the amount of acid liquid component adhering to the surface of the polycrystalline silicon mass, the size of the polysilicon mass, the gas supply temperature, the gas supply wind speed, and the like. In general, the drying time is 10 to 120 minutes, more preferably 30 to 60 minutes.

Drying may be carried out by transferring the polycrystalline silicon mass cleaning body to a drying basket and accommodating it in a dryer. You may continue to carry out the process up to this as it is in the resin basket used for the said washing|cleaning. It is preferable from the viewpoint of energy efficiency that the exhaust of the dryer is reheated as necessary and circulated for drying.

The polycrystalline silicon mass dried as described above may be filled in a resin bag as described above, and the polycrystalline silicon mass package of the present invention may be used. Charging may be performed manually, and may be implemented using a charging apparatus. After filling the resin bag, the opening may be sealed with a heat sealer or the like.

[Example]

Hereinafter, the present invention will be described in more detail by way of Examples, but the present invention is not limited to these Examples. In addition, each physical property value and evaluation in an Example and a comparative example were respectively calculated|required by the following method.

1) Method for measuring the amount of surface nitrate ions and the amount of surface fluorine ions of a polycrystalline silicon mass

100 mL of ultrapure water of the same temperature at room temperature under 25°C and 1 atm is injected into the polycrystalline silicon mass package (a resin bag with a volume of 3.5L, about 5 kg of polycrystalline silicon mass is filled) prepared in Examples and Comparative Examples and sealed. After stirring or shaking for 5 minutes, the nitric acid component and the fluorine component inside the package were eluted into the water.

The eluted water is collected, and the amount of nitrate ions and the amount of fluorine ions (μg) are measured by ion chromatography. Thus, the amount of nitrate ions and the amount of fluorine ions ^{was divided by the surface area S (mm 2} ) of the polycrystalline silicon mass used for measurement to determine the abundance per unit area of each of these ions.

2) Method for Measuring Surface Metal Concentration of Polycrystalline Silicon Mass

About 40 g of the polycrystalline silicon mass was transferred to a 500 ml clean polytetrafluoroethylene beaker, 100 ml of the solution (50 wt%-HF: 10 ml, 70 wt%-nitric acid: 90 ml) was added, followed by extraction at 25° C. for 15 minutes. . The liquid in the beaker and the washing solution obtained by washing the surface of the polycrystalline silicon mass with 100 ml of ultrapure water were transferred to a clean polytetrafluoroethylene beaker to obtain a surface extract of the polycrystalline silicon mass. Thus, the surface extract was evaporated to dryness, and a 3.5 wt%-aqueous nitric acid solution was added to the residue to make a volume of 20.0 ml, the ICP-MS measurement was performed, and Na, Mg, Al, K, Ca, Cr, Fe , Ni, Co, Cu, Zn, W, Ti, and Mo of each surface metal mass was measured. The surface metal concentration of the polycrystalline silicon mass was obtained by dividing the measured value of each surface metal weight by the weight (40 g) of the polycrystalline silicon mass, as a content per unit weight of the polycrystalline silicon mass (pptw).

3) Method for measuring the amount of nitrate ions and fluorine ions present in the polycrystalline silicon mass package

100 mL of ultrapure water of the same temperature at room temperature under 25°C and 1 atm is injected into the polycrystalline silicon mass package (a resin bag with a volume of 3.5L, about 5 kg of polycrystalline silicon mass is filled) prepared in Examples and Comparative Examples and sealed. After stirring or shaking for 5 minutes, the nitric acid component and the fluorine component inside the package were eluted into the water. The eluate was recovered, and the amount of nitrate ions and the amount of fluorine ions (μg) were measured by ion chromatography. Then, by dividing the amount of nitrate ions and the amount of fluorine ions by the filled pore volume of the polycrystalline silicon mass package, the amount of each of these ions (μg/L) with respect to the packed voids was determined. In addition, the filled pore volume (L) of the polycrystalline silicon mass package is calculated by dividing the weight of the filled polycrystalline silicon mass by the density of polycrystalline silicon 2330 kg/m ³ , and the volume of the polysilicon mass is calculated at 25 ° C., under 1 atm. A value obtained by subtracting from the internal volume (L) of the resin bag forming the package was used.

4) Test for occurrence of stains on polycrystalline silicon masses filled in polycrystalline silicon mass package

In order to promote the occurrence of stains in the polycrystalline silicon mass package prepared in Examples and Comparative Examples (a 3.5L resin bag with a volume of about 5 kg of polycrystalline silicon mass), a high-temperature, high-humidity tank with a temperature of 70°C and a humidity of 90% Stored within 7 days. Thereafter, the package was opened and it was observed whether or not unevenness occurred on the surface of each polycrystalline silicon mass that had been filled.

Staining rate = the number of polycrystalline silicon agglomerates that are stained/total number of polycrystalline silicon agglomerates in the package × 100

A: 0% staining rate

B: Stain generation rate is more than 0% and less than 1%

C: Stain generation rate is more than 1% and less than 3%

D: Stain generation rate exceeds 3%

In addition, in all of the polycrystalline silicon lumps subjected to the filling of these packaged bodies, no unevenness was recognized on the surface (staining rate was 0%) by visual observation.

Example 1

A polycrystalline silicon mass obtained by crushing a polycrystalline silicon rod manufactured by the Siemens method by a crushing mechanism (a particle size in which 90 wt% or more of which is within the range of 10 to 60 mm of the major axis) was accommodated in a washing basket, and 20 ° C. of an aqueous hydrofluoric acid solution (containing 8 parts by weight of hydrogen fluoride and 215 parts by weight of nitric acid with respect to 100 parts by weight of water) was immersed in a pickling tank for 10 minutes to be etched, followed by etching in a water washing tank (20° C.) for 10 minutes immersed. The obtained polycrystalline silicon mass cleaning body was accommodated in a heating furnace, and air at 100° C. was supplied and dried at the same heating temperature for 30 minutes. As a result of measuring the surface metal concentration of the dried polycrystalline silicon mass, it was 80 pptw. In addition, as a result of measuring the amount of surface nitrate ions and the amount of surface fluorine ions, it was the result shown in Table 1. Moreover, the surface was visually observed, and it was confirmed that generation|occurrence|production of a stain was not recognized.

About 5 kg of the purified polycrystalline silicon mass obtained by the above was filled in a polyethylene resin bag having a volume of 3.5 L (the filled porosity was 50%: the number of the masses was about 500) to prepare a polycrystalline silicon mass package. This polycrystalline silicon mass package was subjected to a test for occurrence of unevenness on the polycrystalline silicon aggregate to be filled, and the easiness of occurrence of unevenness was evaluated. The results are shown in Table 1.

Example 2

In Example 1, the polycrystalline silicon mass was packaged in the same manner as in Example 1, except that the heating temperature in the heating furnace containing the polycrystalline silicon mass cleaning body was increased to 120°C and the drying time was extended to 60 minutes. sieve was prepared. The obtained polycrystalline silicon mass packaged body was subjected to a test for occurrence of unevenness with respect to the polycrystalline silicon aggregate to be filled, and the easiness of occurrence of unevenness was evaluated. The results are shown together in Table 1.

Comparative Example 1

A polycrystalline silicon mass packaged body was manufactured in the same manner as in Example 1, except that the heating temperature in the heating furnace containing the polycrystalline silicon mass cleaning body was lowered to 80°C in Example 1. The obtained polycrystalline silicon mass packaged body was subjected to a test for occurrence of unevenness with respect to the polycrystalline silicon aggregate to be filled, and the easiness of occurrence of unevenness was evaluated. The results are shown together in Table 1.

Comparative Example 2

In Example 1, in the same manner as in Example 1, except that the heating temperature in the heating furnace containing the polycrystalline silicon mass cleaning body was lowered to 80° C. and the drying time was extended to 60 minutes, the polycrystalline silicon mass washer. A package was prepared. The obtained polycrystalline silicon mass packaged body was subjected to a test for occurrence of unevenness with respect to the polycrystalline silicon aggregate to be filled, and the easiness of occurrence of unevenness was evaluated. The results are shown together in Table 1.

Comparative Example 3

In Example 1, the same as in Example 1, except that the heating temperature in the heating furnace containing the polycrystalline silicon mass cleaning body was lowered to 80° C., and the drying was changed from normal pressure to reduced pressure drying (pressure reduction degree -90 kPa) to prepare a polycrystalline silicon mass package. The obtained polycrystalline silicon mass packaged body was subjected to a test for occurrence of unevenness with respect to the polycrystalline silicon aggregate to be filled, and the easiness of occurrence of unevenness was evaluated. The results are shown together in Table 1.

Comparative Example 4

In Example 1, in the same manner as in Example 1, except that the heating temperature in the heating furnace containing the polycrystalline silicon mass cleaning body was lowered to 80° C. and the drying time was extended to 90 minutes, the polysilicon mass cleaning body was carried out in the same manner as in Example 1. A package was prepared. The obtained polycrystalline silicon mass packaged body was subjected to a test for occurrence of unevenness with respect to the polycrystalline silicon aggregate to be filled, and the easiness of occurrence of unevenness was evaluated. The results are shown together in Table 1.

[Table 1]

Claims (9)

A package in which a polycrystalline silicon mass having a surface metal concentration of 1000 pptw or less is filled in a resin bag, wherein the amount of nitrate ions present inside the package is a polycrystalline silicon mass formed when the package is placed at 25°C and 1 atm pressure A polycrystalline silicon mass packaged body, characterized in that the amount is 50 µg/L or less with respect to the voids. According to claim 1,
A polycrystalline silicon mass package in which the amount of fluorine ions present in the package is 50 µg/L or less with respect to the filled voids of the polysilicon mass formed when the package is placed at 25°C and 1 atm. According to claim 1,
A polycrystalline silicon mass package comprising a polycrystalline silicon mass having a surface metal concentration of 1000 pptw or less and a surface nitrate ion content of 1.0×10 ^-4 µg/mm ^{2 or less, filled in a resin bag.} 4. The method of claim 3,
A polycrystalline silicon mass packaged body with an amount of fluoride ions present on the mass surface of the polycrystalline silicon mass of 1.0×10 ^-4 μg/mm ^{2 or less.} 5. The method according to any one of claims 1 to 4,
A polycrystalline silicon mass package having a filled porosity of 40 to 70% of a resin bag filled with the polycrystalline silicon mass. A polycrystalline silicon mass having a surface metal concentration of 1000 pptw or less and an amount of surface nitrate ions of 1.0×10 ^-4 μg/mm ^{2 or less.} 7. The method of claim 6,
Furthermore, the polycrystalline silicon mass having an amount of surface fluorine ions of 1.0×10 ^-4 μg/mm ^{2 or less.} The method for producing a polycrystalline silicon mass according to claim 6, wherein the polycrystalline silicon mass washing body, which has been acid washed with an aqueous hydrofluoric acid solution, is dried at a heating temperature of 100°C or higher. When the polycrystalline silicon mass obtained by the method according to claim 8 is packaged in a resin bag, the amount of nitrate ions present in the package is filled with the polycrystalline silicon mass formed when the package is placed at 25°C and 1 atmosphere. The method for producing a polycrystalline silicon mass package according to claim 1, characterized in that the voids are filled with a filling amount of 50 µg/L or less.